Disinfectant and method of making

ABSTRACT

A non-toxic environmentally friendly aqueous disinfectant is disclosed for specific use as prevention against contamination by potentially pathogenic bacteria and virus. The aqueous disinfectant is formulated by electrolytically generating silver ions in water in combination with a citric acid. The aqueous disinfectant may include a suitable alcohol and/or a detergent. The aqueous disinfectant has been shown to be very effective at eliminating standard indicator organisms such as  staphylococcus aureus, samonella cholerasuis  and  Pseudomonas aeruginosa.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims benefit of U.S. Patent Provisional applicationSer. No. 60/061,673 filed Oct. 10, 1997. All subject matter set forth inprovisional application Ser. No. 60/061,673 is hereby incorporated byreference into the present application as if fully set forth herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to disinfectants and more particularly to anenvironmentally friendly, non-toxic aqueous disinfectant for specificuse against pathogenic bacteria and viruses.

2. Background of the Invention

The prior art has demonstrated that the presence of copper and silverions in an aqueous solution is useful as a disinfectant. Many in theprior art have used copper and silver ions in an aqueous solution as adisinfectant in water systems such as cooling towers, swimming pools,hot water systems in hospitals, potable water systems, spa pools and thelike.

Typically, copper and silver electrodes were connected to a directcurrent power supply. When the direct current was applied to the copperand silver electrodes, copper and silver ions were generated by anelectrolysis process from the copper and silver ions within the water.In one example of the prior art, water was passed continuously throughan ion chamber having copper and silver electrodes. The water emanatingfrom the ion chamber contained the copper and silver ions generated bycopper and silver electrodes within the ion chamber. The water emanatingfrom the ion chamber containing the copper and silver ions was used as adisinfectant in water systems such as cooling towers, swimming pools,hot water systems in hospitals, potable water systems, spa pools and thelike. The copper and silver ions within the water systems acted as adisinfectant for controlling algae, viruses, bacteria and the like.

U.S. Pat. No. 3,422,183 to Ellison discloses biocide compositionscomprising ultra-violet irradiated silver fluoride solutions containingcolloidal silver resulting from the irradiation and kept in dispersionby a protective colloid, e.g., casein or gelatin, and biocide usesthereof in sline control, against pathogens or other microbes in food orbeverage containers or processing equipment, as an ingredient of woodpreservatives, as a bactericide in paints, as a biocide in syntheticpolymer films, as a sterilant in bandages, and biocide-like uses inother areas.

U.S. Pat. No. 3,702,298 to Zsoldos discloses a method of maintaining ahighly oxidizing aqueous solution intended primarily for treatment ofswimming pool water. A metal having a multiple valence is interacted toa lower valence with oxidizable debris in the solution, and the metal iscontinuously re-oxidized to a higher valence by maintaining in the watera constant excess of an oxidizer bank consisting of a salt of a peroxyacid. Silver, copper and nickel are suitable metals and their salts havegermicidal properties which are greatly increased and the spectrumbroadened by converting the mono salt to a divalent or trivalent salt.

U.S. Pat. No. 4,180,473 to Maurer et al. discloses a method oftransporting metal ions by introducing a metal complex into a mediumcontaining a moiety which demands the metal ion and the complex releasesthe ions in a controlled manner upon demand. The metal complexes have anaqueous proton induced dissociation property represented by asigmoidally-shaped curve on a cartesian coordinate plot of the negativelog of the metal ion concentration versus the negative log of hydrogenion concentration. This dissociation property causes a controlledrelease of metal ion into mediums containing a reacting moiety upondemand for the metal ion. For example, metal working emulsions of oiland water are stabilized by the addition thereto of minor amounts of ametal complex, e.g. disodium monocopper (II) citrate, which at alkalinepH metalworking conditions above about 7 to about 9 releases metalcatons to the emulsions imparting stabilizing characteristics whichprevent emulsion degradation by a number of factors commonly encounteredin metalworking operations. Also, the method is effective in thecontrolled release of metal ions in the normal range of physiologicalpH, i.e. about 4 to 9, for growth controlling action againstmicroorganisms including bacteria, fungi and viruses.

U.S. Pat. No. 4,291,125 to Greatbatch discloses a method and apparatusfor killing plant and animal bacteria and plant viroids by electricallygenerated silver ions. The silver ions serve as germicidal agents ininfection control and are generated by very slow electrical anodiccorrosion of a silver wire located closely adjacent the infection site.In particular, a silver anode and a cathode of non-corroding metal arelocated in an electrolytic nutrient medium with the silver anode beingwithin five millimeters of the infection site, and a direct voltage isapplied to the anode and cathode in a manner passing a positive currentin the microampere range into the silver anode causing it to corrodeslightly and give off silver ions which produce a germicidal environmentabout the infection site.

U.S. Pat. No. 4,385,632 to Odelhog discloses an absorbent body forcollecting blood, feces and urine containing a water-soluble copper saltwhich impedes bacterial growth, prevents the breaking-down of urea intoammonia and complex-binds ammonia so as to prevent the occurrence ofunpleasant odor. Preferably copper acetate is used, in which even theacetate ion has germicidal effect.

U.S. Pat. No. 4,564,461 to Skold et al. discloses mechanical working ofcast iron performed in the presence of an aqueous metal workingcomposition containing an organic copper (II) complex and an ironcorrosion inhibitor. An aqueous concentrate, which after dilution withwater is suitable for application in mechanical working of cast iron,contains 1-50% copper (II) complex with such a Cu₂+ content of 0.5-20%,1-50% iron corrosion inhibitor, 0-50% lubricant, 0-20% pH-regulators,bactericides and solubilizing agents and 10-70% water.

U.S. Pat. No. 4,608,183 to Rossmoore discloses antimicrobial mixtures ofisothiazolones and a metal complex with a polyfunctional ligand whichare synergistic. The mixtures particularly include mixtures of amonocopper disodium citrate as the ligand and a 5-x-2-lower alkyl4-isothiazolin-3-one wherein x is a halo or hydrogen group as theisothiazolone. The compositions are particularly useful for metalcutting fluids wherein long duration antimicrobial activity is desired.

U.S. Pat. No. 4,666,616 to Rossmoore discloses synergisticanti-microbial compositions containing a mixture of a metal complex of apolyfunctional organic liquid and a biocidal composition which containsor releases a lower aldehyde containing 1 to 5 carbon atoms. Thecompositions are particularly useful as metal working fluids at alkalinepH and have a broad spectrum of activity against fungi and bacterial.

U.S. Pat. No. 4,708,808 to Rossmoore discloses synergisticanti-mircrobial compositions containing a mixture of a metal complex ofa polyfunctional organic ligand and a biocidal composition whichcontains or releases a lower aldehyde containing 1 to 5 carbon atoms.The compositions are particularly useful as metal working fluids atalkaline pH and have a broad spectrum of activity against fungi andbacteria.

U.S. Pat. No. 4,780,216 to Wojtowicz discloses a sanitizing compositionconsisting essentially of a mixture of a calcium hypochlorite compoundand a peroxydisulfate compound having the formula: M_(x)S₂O₈ where M isan alkali metal or alkaline earth metal, and x is 1 or 2 is employed intreating water to improve pH control and provide increased removal oforganic materials. The compositions provide improved sanitation of waterin swimming pools, spas, and cooling towers by efficiently oxidizingorganic impurities while helping to minimize the increase in the pH ofthe water. This permits a reduction in the amount and frequency ofaddition of acidic compounds such as hydrochloric acid to the waterbodies. Further, the incorporation of additives such as algaecides,dispersant, and clarifying agents provides for significant improvementsin water quality as evidenced by sparkling pure water.

U.S. Pat. No. 4,915,955 to Gomori discloses a concentrate with anunlimited shelf-life, which can be mixed with hydrogen peroxide at aratio of 1:99 to 1:199 to become an effective disinfectant, is obtainedwhen a viscous solution of inorganic acid, with a pH less than or equalto 1.6, is mixed with a silver salt compound or a colloidal silvercompound at 50° to 66° C. The mixture is further combined at roomtemperature with other inorganic acid(s) to reach a total of 100 ginorganic acid(s) per liter of water at room temperature, an organicacid stabilizer is added and the mixture is homogenized. Theconcentrate, during storage, remains homogeneous and crystal-clear.

U.S. Pat. No. 4,933,178 to Capelli discloses a medical device with anantimicrobial coating that is safe, effective, photostable and readilymanufacturable produced by applying a composition to at least one bodyfluid-contacting surface of the device such that a solid coating isprovided on that surface, the coating composition comprising anoligodynamic metal salt of a sulfonylurea, a polymeric material, atleast one acid compound selected from the group consisting of awater-soluble carboxylic acid and water-insoluble carboxylic acid, and acarrier liquid in which foregoing components are soluble. Theantimicrobial coating accommodates variation in the release ofantimicrobial metal ions as a function of the intended use for a medicaldevice to which the coating is applied.

U.S. Pat. No. 5,017,295 to Antelman discloses a method or methods ofcontrolling the growth of bacteria in the water of swimming pools and/orindustrial water supplies by adding to the water a specifiedconcentration of a stable divalent silver compound. The invention hasthe advantage over chlorination in that it is odorless and non-volatile.It furthermore is superior to monovalent silver compounds as thesecompounds do not decompose in the presence of light and resistprecipitation by halides and form divalent soluble complexes which inthe monovalent state are invariably insoluble solids.

U.S. Pat. No. 5,073,382 to Antelman discloses a solid alkalinebactericidal compositions suitable for compounding alkaline end productssuch as food and dairy cleaners and surgical scrubbing soaps, formed bythe neutralization of acid stabilized inorganic divalent silvercomplexes and capable of effecting 100% kills upon cultures of anaerobicbacteria colonies of 100 K/cc. within 5 minutes.

U.S. Pat. No. 5,078,902 to Antelman discloses divalent silver halidesproviding a source for divalent bactericidal silver ions in the presenceof persulfate. The halides are especially effective when applied towater used in industrial cooling installations, hot tubs and swimmingpools and will conform to stringent EPA requirements for waters utilizedfor bathing as in tubs and pools of 100% kills of 100 K/cc E. Colicoliforms within 10 minutes, exemplary of which are the chloride andbromide which give 100% kills within 5 minutes. The halides, of course,can be used in salty water since they are solids immune from halideaction that would otherwise precipitate soluble divalent silver fromsolution.

U.S. Pat. No. 5,089,275 discloses solid bactericidal compositions basedon divalent silver (Ag(II)) as the active sanitized agent. Thecompositions are prepared by reacting acid liquid Ag(II) complexes withanhydrous calcium sulfate so as to form a solid matrix in which thebactericide is entrapped in the resulting hydrated calcium sulfate.Optimum compositions are described consisting of Ag(II) of solid (byweight) to liquid (by volume) is 5:2. The resulting solid bactericidescan be used in water cooling installations. They are capable of causing100% kills within 10 minutes of E. Coli conforms in conformity with EPAprotocols, allowing them to qualify as swimming pool and hot tubsanitizers. Since the compositions are based on calcium sulfate, theyare also suitable as mineralizers, thus providing a dual function.

U.S. Pat. No. 5,332,511 to Gay et al. discloses a process for sanitizingwater in swimming pools, spas and hot tubs whereby the level of bacteriain said water is lowered comprising treating said water with abactericidal effective amount of a combination of diisodecyl dimethylammonium chloride and copper (II) ions, the concentration of diisodecyldimethyl ammonium chloride in said water being less than about 60 partsper million parts of water by weight and treating said water at leastintermittently with an oxidant selected from the group consisting ofavailable chlorine and ozone.

U.S. Pat. No. 5,364,649 to Rossmoore et al. discloses activity ofantimicrobial compounds selected from isothiazolones and compounds whichrelease formaldehyde enhanced with a metal complex of a loweralkanolamine, particularly copper (cupric) trietha-iolamine. Theenhancement is particularly useful in metalworking fluids.

U.S. Pat. No. 5,373,025 to Gay discloses a sanitizer compositioncomprising a bactericidal effective amount of the combination of (a) aquaternary ammonium compound selected from the group consisting of(hydrogenated tallow) 2-ethylhexyl dimethyl ammonium salt, dicocodimethyl ammonium salt, and mixtures thereof; and (b) a copper (II) ionsource.

U.S. Pat. No. 5,382,337 to Wlassics et al. discloses a process foroxidizing organic materials or compounds in aqueous phase, with hydrogenperoxide and in the presence of ferrous ions FE-(II), and optionallycupric ions cu-(II), carried out under irradiation with artificialvisible light.

U.S. Pat. No. 5,464,559 to Marchin et al. discloses a compositionprovided for treating drinking water for disinfecting and/or removingiodide. The composition utilizes resin bound silver ions. For performingthe disinfection or iodide removal with minimal release of silver ionsinto the water being treated, a chelating resin having iminodiacetatechelating groups is employed, and the resin is loaded with not over 0.5mole of silver ions per mole of iminodiacetate.

U.S. Pat. No. 5,503,840 to Jacobson et al. discloses an antimicrobialcomposition of titanium dioxide, barium sulfate, zinc oxide particles,and mixtures thereof having successive coatings of silver, in some casesa coating of zinc and/or copper compounds such as zinc oxide, copper(II) oxide and zinc silicate; silicon dioxide; alumina; and a dispersionaid such as dioctyl azelate.

U.S. Pat. No. 5,510,109 to Tomioka et al discloses an antibacterial andantifungal composition which comprises an antibacterial and antifungalmaterial carried on a porous particle carrier. Preferably, the porousparticle carrier is a silica gel particle. The antibacterial andantifungal material is at least one metal complex salt, and can containplant extracts and the like in addition to the metal complex salt. Atleast a portion of the surface of the above-mentioned carrier having theantibacterial and antifungal composition can be coated with a coatingmaterial.

Unfortunately, these copper and silver ions within an aqueous solutionhave only a limited stable ionic life. After a limited time, the copperand silver ions form complexes with other elements thus diminishing theconcentration of the copper and silver ions within the aqueous solution.Accordingly, the aqueous solution had to be replenished with copper andsilver ions to maintain the concentration of the copper and silver ionswithin the aqueous solution. The aqueous solution may be replenishedwith copper and silver ions by constantly circulating the aqueoussolution thorough the ion chamber.

The present invention provides an aqueous disinfectant solution having astable ionic form having an extended useful shelf-life. The extendeduseful shelf-life of the aqueous disinfectant solution enables theaqueous disinfectant solution to be packaged in an aqueous concentrateform.

Therefore, it is an object of the present invention to provide animproved disinfectant and the method of making comprising an aqueousdisinfectant for specific use as prevention against contamination bypotentially pathogenic bacteria and virus and antifungal properties.

Another object of this invention is to provide an improved disinfectantand the method of making which is an effective disinfectant foreliminating standard indicator organisms such as staphylococcus aureus,samonella cholerasuis and Pseudomonas aeruginosa.

Another object of this invention is to provide an improved disinfectantand the method of making which is a non-toxic, environmentally friendlyaqueous disinfectant.

Another object of this invention is to provide an improved disinfectantand the method of making which comprises a stable ionic formulationhaving an extended useful shelf-life.

Another object of this invention is to provide an improved disinfectantand the method of making which may be packaged in a concentrated aqueousform.

Another object of this invention is to provide an improved disinfectantand the method of making which may be electrolytically generated in abatch process or a continuous process.

Another object of this invention is to provide an improved disinfectantand the method of making which is electrolytically generated in aneconomical manner.

Another object of this invention is to provide an improved disinfectantand the method of making which is suitable for use with an alcoholand/or a detergent.

Another object of this invention is to provide an improved disinfectantand the method of making which may be used on exposed and/orcontaminated surfaces to kill bacteria, virus, fungi and othermicro-organisms.

Another object of this invention is to provide an improved disinfectantand the method of making which may be used on contaminated open woundsand tissue, dermal wound sites and/or lesions of living organisms suchas animals and humans.

Another object of this invention is to provide an improved disinfectantand the method of making which may be used on exposed surfaces in foodprocessing plants, residential, hospital, restaurants, public facilitiesand the like.

The foregoing has outlined some of the more pertinent objects of thepresent invention. These objects should be construed as being merelyillustrative of some of the more prominent features and applications ofthe invention. Many other beneficial results can be obtained by applyingthe disclosed invention in a different manner or modifying the inventionwith in the scope of the invention. Accordingly other objects in a fullunderstanding of the invention may be had by referring to the summary ofthe invention, the detailed description describing the preferredembodiment in addition to the scope of the invention defined by theclaims taken in conjunction with the accompanying drawings.

SUMMARY OF THE INVENTION

A specific embodiment of the present invention is described and shown inthe attached Detailed Description. For the purpose of summarizing theinvention, the invention relates to an improved non-toxicenvironmentally friendly aqueous disinfectant for use as a preventionagainst contamination by potentially pathogenic bacteria, virus andfungi. The improved aqueous disinfectant is suitable for use on exposedsurfaces. In addition, the improved aqueous disinfectant is suitable foruse on dermal wound sites and lesions of living organisms such asanimals and humans. The aqueous disinfectant is pH neutral.

The improved aqueous disinfectant comprises an aqueous solution ofsilver citrate wherein the silver is electrolytically generated in asolution of citric acid and water. The electrolytically generated silverforms an organic metal complex with the citric acid such as a chelatedorganic metal complex with the citric acid. In one example of theinvention, the solution of citric acid and water comprises approximately5.0% to 10.0% citric acid by volume. The silver citrate formed by theelectrolytically generated silver has a concentration in excess of0.0005% by volume.

In another example of the invention, the invention is incorporated intoan aqueous disinfectant in a concentrated form having an extendedshelf-life comprising an aqueous solution of silver citrate wherein thesilver is electrolytically generated in a solution of citric acid inwater. The electrolytically generated silver has a concentration of inexcess of 0.05% by volume.

The aqueous disinfectant may be combined with an alcohol such as ethylalcohol (ETOH) and/or a detergent such as sodium dodecyl sulfate.

The invention is also incorporated into the process of making thedisinfectant comprising the step of electrolytically generating silverin a solution of citric acid and water to formed an aqueous solution ofsilver citrate. The process may include creating a solution ofapproximately 5.0% to 10% citric acid in water by volume. A positivesilver electrode is spaced relative to a negative electrode for enablingthe solution to be located therebetween. A potential difference isapplied to the positive and negative electrodes to establish a flow ofsilver ions between the positive and negative electrodes for enablingthe silver ions to react with the citric acid to form silver citratethereby.

The invention is also incorporated into the process of making silvercitrate, comprising the step of electrolytically generating silver in asolution of citric acid and water to formed an aqueous solution ofsilver citrate.

The foregoing has outlined rather broadly the more pertinent andimportant features of the present invention in order that the detaileddescription that follows may be better understood so that the presentcontribution to the art can be more fully appreciated. Additionalfeatures of the invention will be described hereinafter which form thesubject of the invention. It should be appreciated by those skilled inthe art that the conception and the specific embodiments disclosed maybe readily utilized as a basis for modifying or designing otherstructures for carrying out the same purposes of the present invention.It should also be realized by those skilled in the art that suchequivalent constructions do not depart from the spirit and scope of theinvention.

BRIEF DESCRIPTION OF THE DRAWINGS

For a fuller understanding of the nature and objects of the invention,reference should be made to the following detailed description taken inconnection with the accompanying drawings in which:

FIG. 1 is a diagram of a first process of making the disinfectant of thepresent invention;

FIG. 2 is a diagram of a second process of making the disinfectant ofthe present invention;

FIG. 3 is an enlarged detailed view of the ion chamber of FIGS. 1 and 2;

FIG. 4 is an enlarged detailed view of an ion chamber suitable formaking the disinfectant of the present invention in a batch process;

FIG. 5 is a table illustrating the shelf-life tests for initial samplingintervals;

FIG. 6 is a table illustrating the shelf-life tests for secondarysampling intervals;

FIG. 7 is a table illustrating the efficacy tests against samonellacholerasuis;

FIG. 8 is a table illustrating the efficacy tests against staphylococcusaureus; and

FIG. 9 is a table illustrating the efficacy tests against Pseudomonasaeruginosa.

Similar reference characters refer to similar parts throughout theseveral Figures of the drawings.

DETAILED DISCUSSION

Process of Making

FIG. 1 is a diagram of a first process 10 of making the disinfectant 14of the present invention. The first process 10 is shown as a continuousprocess of making the disinfectant 14. It should be understood that thefirst process 10 of FIG. 1 is only an example of a process and numerousother variations and/or processes may be utilized to make thedisinfectant 14 of the present invention.

The disinfectant 14 may be used immediately for any suitable applicationsuch as a disinfectant in a water system including cooling towers, hotwater systems, potable water systems, or any other suitable applicationor surface.

The first process 10 comprises a water input conduit 16 for introducingwater 18 from a water source (not shown) to a water treatment unit shownas a reverse osmosis unit 20. The reverse osmosis unit 20 passes thewater 18 from the water input conduit 16 through a semi-permeablemembrane (not shown) for removing impurities from the water. Althoughthe water treatment unit is shown as a reverse osmosis unit 20 it shouldbe understood that various water treatment units may be employed withinthe process shown in FIG. 1. Preferably, the water 18 emanating from thereverse osmosis unit 20 is deionized medically pure water.

The water 18 emanating from the reverse osmosis unit 20 is directed to avalve 30 through a conduit 31. The valve 30 directs the water 18 thougha conduit 32 to a flow control injector 40. A citric acid tank 50contains concentrated citric acid. The concentrated citric acid isdirected by a conduit 51 to a metering valve 60 for metering theconcentrated citric acid into the flow control injector 40. The flowcontrol injector 40 mixes the concentrated citric acid with the water 18to provide a dilute citric acid solution 62. The metering valve 60controls the concentration of the citric acid within the water 18. Thediluted citric acid solution 62 is directed by a conduit 62 into an ionchamber 70.

FIG. 3 is an enlarged detailed view of the ion chamber 70 of FIG. 1. Theion chamber 70 includes a positive and a negative electrode 71 and 72.The positive and negative electrodes 71 and 72 are located in a spacedapart position for enabling the diluted citric acid solution 62 to passbetween the positive and negative electrodes 71 and 72. Each of thepositive and negative electrodes 71 and 72 is fabricated from elementalsilver. Preferably, the positive and negative electrodes 71 and 72 areformed from 99.9999% pure elemental silver.

A direct current power supply 80 includes a positive and a negativeconductor 81 and 82 connected to the positive and negative electrodes 71and 72. The positive and negative electrodes 71 and 72 are spaced aparta suitable distance such as 2.0 to 8.0 centimeters to allow an ioniccurrent flow between the positive and negative electrodes 71 and 72.

Upon energizing the direct current power supply 80, an ion current flowsbetween the positive and negative electrodes 71 and 72. The direct ioncurrent flow between the positive and negative electrodes 71 and 72produces electrolytically free silver ions within the diluted citricacid solution 62. The silver ions react with the citric acid in thediluted citric acid solution 62 to produce the disinfectant 14 of thepresent invention.

The disinfectant 14 is directed by a conduit 86 to a settling tank 90.The settling tank 90 includes an overflow conduit 91 and a drain conduit92. The disinfectant 14 exits the settling tank 90 through the overflowconduit 91. Any precipitated materials from the disinfectant 14 withinthe settling tank 90 fall to the bottom of the settling tank 90. Theprecipitated materials at the bottom of the settling tank 90 may beremoved through the drain conduit 92 to a purge tank 100. Theprecipitated materials in the purge tank 100 may be recycled.

The disinfectant 14 exiting through the overflow conduit 91 from thesettling tank 90 is directed to a particle filter 110. Although theparticle filter 110 may be any suitable filter, preferably the particlefilter 110 is a submicron filter. The filtered disinfectant 14 isdirected to a valve 120 by a conduit 121. The valve 120 directs thefiltered disinfectant 14 to a conduit 122 for discharge from the firstprocess 10.

The filtered disinfectant 14 discharged from conduit 122 may be usedimmediately for any suitable application such as a disinfectant in awater system or any other suitable application. In the event a greaterconcentration of the disinfectant 14 is desired, the disinfectant 14 maybe recirculated for increasing the concentration of the disinfectant 14.

FIG. 2 is a diagram of a second process 10A of making the disinfectant14 of the present in a concentrated form. The second process 10A isshown as a recirculating process of making the disinfectant 14 and forincreasing the concentration of the disinfectant 14. In the concentratedform, the disinfectant 14 may be bottled for use at a later time. Itshould be understood that the second process 10A of FIG. 2 is only anexample of a process and numerous other variations and/or processes maybe utilized to make the disinfectant 14 of the present invention.

In the second process 10A shown in FIG. 2, the valve 30 and 120 are moveinto positions opposite to the positions shown in FIG. 1. The valve 120directs the filtered disinfectant 14 to a conduit 123. The conduit 123is connected through a conduit 130 to the conduit 32 of the valve 30.

The valve 30 directs the filtered disinfectant 14 though the conduit 32to the flow control injector 40. Additional concentrated citric acid isdirected through the metering valve 60 into the flow control injector40. The flow control injector 40 mixes the concentrated citric acid withthe filtered disinfectant 14 to increase the concentration of the citricacid solution 62A.

The citric acid solution 62A is directed into an ion chamber 70 toproduce additional silver ions within the citric acid solution 62A. Thesilver ions react with the citric acid in the citric acid solution 62Ato increase the concentration of the disinfectant 14. The disinfectant14 is passed through the settling tank 90 to exit through the overflowconduit 91. The disinfectant 14 is filtered by the particle filter 110and is directed to the valve 120 by the conduit 121.

The valve 30 and 120 are maintained in positions shown in FIG. 2 tocontinue to recirculate the disinfectant 14 for increasing theconcentration of the disinfectant 14. Upon obtaining the desiredconcentration of the disinfectant 14, the valve 120 may be moved to theposition shown in FIG. 1 to discharge the disinfectant 14 from theconduit 122.

FIG. 4 is an enlarged detailed view of an ion chamber 170 suitable formaking the disinfectant of the present invention in a batch process. Theion chamber 170 includes a positive and a negative electrode 171 and172. Each of the positive and negative electrodes 171 and 172 isfabricated from 99.9999% pure elemental silver.

The positive and negative electrodes 171 and 172 are located in a spacedapart position for enabling the citric acid solution 162 to pass betweenthe positive and negative electrodes 171 and 172. Preferably, thepositive silver electrode 171 is spaced relative to a negative electrode172 a distance sufficient to enable silver ion flow therebetween. Thespacing of the positive and negative electrodes 171 and 172 has beenshown in an exaggerated fashion in FIG. 4. Preferably, a spacing ofapproximately 2.0 to 8.0 mm. has been found to be suitable for the aboveconcentration of citric acid and water.

A direct current power supply 180 includes a positive and a negativeconductor 181 and 182 connected to the positive and negative electrodes171 and 172. Upon energizing the direct current power supply 180, an ioncurrent flows between the positive and negative electrodes 171 and 172.The direct ion current flow between the positive and negative electrodes171 and 172 produces electrolytically free silver ions within the citricacid solution 162. The silver ions react with the citric acid in thecitric acid solution 162 to produce the disinfectant 14 of the presentinvention.

The process of making a disinfectant comprises electrolyticallygenerating silver ions in a solution of citric acid and water to form anaqueous solution of silver citrate. Preferably, the solution of citricacid and water comprises a solution of approximately 5.0% to 10% citricacid in water by volume. A potential difference of 12 volts to 50 voltsprovides a flow of silver ions in the range of 0.1 amperes to 0.5amperes per square inch. A more fuller explanation of the content of thesolution within the ion chamber 170 will be described in greater detailhereinafter.

The prior art has established in that the generation of both silver ionsand copper ion in water provides the best disinfectant properties. Thecombination of silver ions and copper ions provides superiordisinfecting properties than either silver ions alone or copper ionsalone. This synergistic effect of silver ions and copper ions in waterhas been well established by the prior art.

In contrast to this established prior art, the disinfectant of thepresent invention is formed in a solution of citric acid and waterrather than water alone. Additionally, the disinfectant of the presentinvention has superior properties with only silver ions alone ratherthan the combination of both silver ions and copper ions. The silverions of the present process react with the citric acid to form a silvercitrate. The silver citrate provides superior disinfectant propertiesover the prior art process of generating silver and copper ions inwater.

In further contrast to the established prior art, the disinfectant ofthe present invention has a stable ionic form having an extended usefulshelf-life. The useable shelf-life of the disinfectant of the presentinvention enables the aqueous disinfectant solution to be packaged in anaqueous concentrate form.

Composition

The improved disinfectant is an aqueous solution of silver citratewherein the silver is electrolytically generated in a solution of citricacid and water. The silver citrate formed in accordance with the aboveprocess has different characteristics than other forms of silvercitrate.

Concentrations of 0.1% silver citrate by volume have been formulated inaccordance with the above process. A concentration of 0.1% silvercitrate by volume corresponds to 1000 parts per million (ppm). Theconcentration of 0.1% silver citrate was formed in a solution of citricacid and water comprises approximately 10.0% citric acid by volume.Higher concentration of the silver citrate are believed to be obtainableby the above process. It appears the higher the concentration of citricacid in water, the higher the concentration of silver citrate formed bythe above process.

The Merck Index, Eleventh Edition (1989) page 1348 states that silvercitrate is soluble in 3500 parts water. A concentration of 1 to 3500corresponds to 285 parts per million (ppm). Obviously, the silvercitrate formed in accordance with the above process has differentsolubility than other forms of silver citrate.

Nuclear magnetic resonance tests (1H NMR) were preformed on the silvercitrate formed in accordance with the above process and a blank citricacid sample. The samples showed an overwhelming excess of citric acid,with little or no other anions present. It is postulated the Ag must bein the form of the cation Ag+ complexed with the citric acid. It istheorized the empty 5s orbital of Ag+ overlaps with the delocalized πbond on one of the carboxyl groups of citric acid. The citric acid anionis the counterion for this complex ion (Ag(CA)x)+l.e. (CA). CA is citricacid or is (C₆H₈O₇—H₂O). Another possibility is a zwitterion, where thenegative charge is on the complex itself, (Ag+CA−) where the totalcharge of the complex is neutral. Either or both of these species mayexist in the silver citrate formed in accordance with the above process.Multiple complexation to Ag+ is also possible.

A second formulation of the improved disinfectant of the presentinvention includes the addition of an alcohol. In one example of thesecond formulation of the improved disinfectant, ethyl alcohol (ETOH) isadded in an approximate amount of 20% by volume. However, it should beunderstood that other types of alcohols may be added to the secondformulation of the improved disinfectant of the present invention.

A third formulation of the improved disinfectant of the presentinvention includes the addition of a detergent. In one example of thethird formulation of the improved disinfectant, sodium dodecyl sulfateis added in an approximate amount of 0.1% by volume.

Shelf-Life Study

The copper and silver ions in the prior art aqueous solution have only alimited stable ionic life. After a limited time, the copper and silverions in the prior art aqueous solution form complexes with otherelements thus diminishing the concentration of the copper and silverions within the aqueous solution.

A significant difference of the disinfectant of the present invention isthe stable life of the silver citrate. The present invention provides anaqueous disinfectant solution having a stable ionic form having anextended useful shelf-life. The extended useful shelf-life of thedisinfectant of the present invention enables the disinfectant to bepackaged in an aqueous concentrate form.

A series of tests was preformed on the following formulations.

1. Silver and Citric Acid (1.0% citric acid solution/pH 6.0)

2. Silver and Citric Acid (5.0% citric acid solution/pH 6.0)

3. Silver and Citric Acid (10% citric acid solution/pH 6.0)

The silver and citric acid formulations were prepared using 100/100silver:silver electrodes. The electrodes were immersed in 1.0, 5.0 and10% citric acid solutions and a current was applied for approximatelytwo hours. The solutions were stored for 24 hours to allow forprecipitation. The solutions were filtered using #2 Whatman filterpaper. The final pH was adjusted to 6.0 with sodium carbonate and sodiumbicarbonate.

FIG. 5 is a table illustrating the results of the shelf-life test forthe initial shelf-life sampling intervals. The initial intervals for theinitial shelf-life sampling intervals of the disinfectant were 1 week, 2weeks, 3 weeks and 4 weeks. FIG. 5 illustrates that silver citrate isnot stable at high concentrations in the 1.0% citric acid solution. The300 ppm silver citrate did not remain in the 1.0% citric acid solution.However, the 300 ppm silver citrate was stable in the 10% citric acidsolution.

FIG. 6 is a table illustrating the results of the shelf-life test forsecondary shelf-life sampling intervals. The secondary intervals for thesecondary shelf-life sampling intervals of the disinfectant were 0weeks, 7 weeks, 14 weeks and 21 weeks. FIG. 6 also illustrates thatsilver citrate is not stable at high concentrations in the 1.0% citricacid solution. Conversely, the silver citrate was stable in both the 5%and 10% citric acid solutions.

The results seen in FIG. 6 for week 21 confirm the stability of thesilver citrate in the 5.0% and 10% citric acid solutions. The stabilityof the silver citrate in the 1.0% citric acid solution experiencedsignificant reductions during the last phase of the study. The minimumconcentration of the citric acid solution is therefore some valuegreater than 1.0% and less than 5.0%. The maximum concentration of thecitric acid in the aqueous solution has not been determined by test.

However, it is believed that the maximum concentration of the citricacid in the aqueous solution much greater than 10.0%. It is also evidentfrom these results, that the higher the concentration of the citric acidin the aqueous solution, the greater the concentration of silver ionsthat can be stabilized.

Laboratory Study

In order to establish the effectiveness of the improved disinfectant ofthe present invention, laboratory tests were performed against varioustest microorganisms. The test microorganisms considered were (a)pseudomonas aeruginosa strain ATCC 15442, (b) Salmonella cholerasuisstrain ATCC 10708 and (c) Staphylococcus aureus strain ATCC 6538.

The inoculum level for each of the test microorganisms were establishedin a similar manner. Test strains were grown individually at 35° C. for24 hr. The cells were harvested by centrifugation at 10,000×g for 10minutes and washed twice with Butterfield's Phosphate Buffer (BPB of pH7.2). The cells were resuspended in the Butterfield's Phosphate Bufferto obtain a cell suspension of approximately 1.0×10⁸ CFU/mL for eachmicroorganism (target inoculum levels were approx. 10⁶ in the final testsolution).

The test microorganisms considered were tested at uniform samplingintervals, The sampling intervals selected were (a) 15 seconds (ethanoltrials only), (b) 1 minute, (c) 5 minutes, (d) 10 minutes and (e) 30minutes.

Five compounds were tested against the test microorganisms. The fivecompounds tested were (a) silver and citric acid (4.27 ppm in a 0.1%citric acid solution), (b) copper and citric acid (4.07 ppm in a 0.1%citric acid solution), (c) citric acid (0.1% citric acid solution), (d)silver (4.08 ppm), citric acid (0.1%) and ethanol (20%) and (e) Ethanol(20%).

The silver and citric acid (4.27 ppm in a 0.1% citric acid solution) wasprepared using 100/100 silver:silver electrodes. The electrodes wereimmersed in a 0.1% citric acid solution and current was applied forapproximately two hours. The solution was stored for 24 hours to allowfor precipitation. The solution was filtered using No. 2 Whatman filterpaper. The final pH was adjusted to 7.0. The concentration tested had asilver concentration of 4.27 mg/L.

The copper and citric acid (4.07 ppm in a 0.1% citric acid solution) wasprepared using 100/100 copper:copper electrodes. The electrodes wereimmersed in a 0.1% citric acid solution and current was applied forapproximately two hours. The solution was stored for 24 hours to allowfor precipitation. The solution was filtered using #2 Whatman Filterpaper. The final pH was adjusted to 7.0. The concentration tested had acopper concentration of 4.07 mg/L (as measured by ICAP).

The citric acid (0.1% citric acid solution) was prepared using deionizedwater. The pH was adjusted to 7.0.

The silver (4.08 ppm), citric Acid (0.1%) and ethanol (20%) was preparedusing 100/100 silver:silver electrodes. The electrodes were immersed ina 0.1% citric acid solution and current was applied for approximatelytwo hours. The solution was stored for 24 hours to allow forprecipitation. The solution was filtered using #2 Whatman filter paper.The final pH was adjusted to 7.0. The solution was diluted with ethanolto yield a concentration of 4.08 mg/L silver in a 20% ethanol solution.

The Ethanol (20%) was prepared with by diluting Reagent grade ethanolwith deionized water to make the appropriate dilution.

The test microorganisms were tested in accordance with the followingtest procedures. Duplicate trials were conducted for each test variable.Ninety nine volumes of the test solutions in 250 mL Erlenmeyer flaskswere prepared from sterilized deionized water. The solutions wereinoculated separately with one mL of 24 hour culture from each of thetest strains to yield a flask inoculum level of approximately 1.0×10⁶CFU/mL. The actual count for each of the microorganisms are set forth inFIGS. 7-9.

Solutions were mixed well and kept under constant agitation. Samples of1.0 mL were removed at the above specified time intervals and placedinto 9.0 mL Neutralization Broth media (Difco) to yield an initialdilution of 1:10. All samples were serially diluted in the Butterfield'sPhosphate Buffer solution (BPB) and plated onto Tryptic Soy Agar (TSA)in duplicate using the pour plate technique. Percent reductions werecalculated for each test solution against each test strain.

The results of the laboratory study can be seen in FIGS. 7-9. For alltests which utilized either copper or silver ions, concentratedsolutions were prepared 24 hours prior to the beginning of the study.Solutions were filtered and determinations for ion content were made.From these stock solutions (copper ion concentration as measured by ICAPand silver ion concentration as measured by Atomic Absorption analysis),final working solutions were made. The target ion concentration for bothcopper and silver was 5.0 mg/L.

FIG. 7 is a table illustrating the efficacy tests against samonellacholerasuis. The trials that utilized 20% ethanol showed a slow, butcomplete disinfection. The ethanol solution has an approximate 1.0 log₁₀reduction after one minute. Near complete disinfection was seen after 30minutes of contact time. Of the three organisms tested, samonellacholerasuis was the one most effected by the ethanol disinfectant. Thecopper:citric acid was not effective in disinfecting samonellacholerasuis at any of time periods. The citric acid solution wasslightly more effective in reducing the number of samonella cholerasuis,achieving a 1.0 log₁₀ reduction at the 30 minute time period. Bothsilver:citric acid and silver:citric acid with ethanol exhibited a 6.0log₁₀ reduction over the course of the 30 minute trial. Thesilver:citric acid solution showed a 5.0 log₁₀ reduction within thefirst 5 minutes and a greater 6.0 log₁₀ reduction at the 10 minute timeperiod. Silver:citric acid with ethanol appeared to be the mosteffective, exhibiting a 2.36 log₁₀ reduction within in the first minuteand a greater than 6.0 log₁₀ reduction within the first 5 minutes ofcontact.

FIG. 8 is a table illustrating the efficacy tests against staphylococcusaureus. This table indicates a different reaction for the 20% ethanolagainst staphylococcus aureus as compared to samonella cholerasuis. Nosignificant reduction was seen between 15 seconds and 30 minutes.Neither citric acid nor copper:citric acid was effective againststaphylococcus aureus. Neither of the aforementioned formulas were ableto significantly reduce the number of staphylococcus aureus organismspresent within the 30 minute time period. However, both silver:citricacid and silver:citric acid with ethanol exhibited a 6.0 log₁₀ reductionover the course of the 30 minute trial. The silver:citric acid solutionshowed a 3.0 log₁₀ reduction within the first 10 minutes and a greaterthan 6.0 log₁₀ reduction at the end of 30 minutes. Silver:citric acidwith ethanol appeared to be the most effective, exhibiting a 2.36 log₁₀reduction within the first minute and a greater than 6.0 log₁₀ reductionwithin the first 5 minutes of contact.

FIG. 9 is a table illustrating the efficacy tests against Pseudomonasaeruginosa. The seen in this table for Pseudomonas aeruginosa, indicatesimilar results as those seen for that used staphylococcus aureus. Forthe 20% ethanol trials, no significant reduction was seen between 15seconds and 30 minutes. This same trend was recorded for citric acid andcopper:citric acid.

Both silver:citric acid and silver:citric acid with ethanol exhibitednear or greater than 6.0 log₁₀ reductions over the course of the 30minute trial. The silver:citric acid solution showed a 2.49 log₁₀reduction at the 10 minute time period and a greater than 5.70 log₁₀reduction at the end of 30 minutes. Silver citric acid with ethanolshowed the best disinfection against pseudomonas aeruginosa, mirroringthe results seen with the other two organisms. A greater than 6.0 log₁₀reduction was recorded at the 5 minute sampling period.

Field Trial Results

The improved disinfectant has been tested in preliminary veterinaryfield trials to establish the effectiveness of the present invention.The veterinary field trial test were conducted by licensed veterinarianson equine species. The improved disinfectant was tested on contaminatedopen, non-healing tissue and wounds. The open, non-healing wounds weretreated with wet dressings or by spraying the improved disinfectant ontothe wound.

The disinfectant has been tested on dermal lesions both contaminated andinfected with gram negative and gram positive bacteria. The results haveshown that this formulation exhibits superior performance as compared toavailable disinfectant products currently on the market. Thedisinfectant formulation has shown to be very efficacious for irrigatingdeep wounds and abscesses without damage to tissue. Decreased healingtime and reduction in scar formation have been observed repeatedlyduring the study. The disinfectant appears to promote healthygranulation without excessive fibrosis.

The disinfectant has been used as a surface disinfectant and thereforehas shown best results with extended contact with the contaminatedtissue. On surface wounds, best results are obtained with “wet dressing”or frequent spray applications for dermal surfaces not amenable toapplied dressing. Drained abscesses are flushed, the disinfectantsolution is held in the cyst, then drained and again filled and agitatedfor 2-3 minutes before allowing to drain. Deep wounds closed with drainshave shown rapid healing time and reduced draining when flushed with thedisinfectant. An additional use for the disinfectant may be as a uterineflush for bacterial and/or fungal/yeast infection. Preliminary resultswith this application have shown to be very promising.

The present disclosure includes that contained in the appended claims aswell as that of the foregoing description. Although this invention hasbeen described in its preferred form with a certain degree ofparticularity, it is understood that the present disclosure of thepreferred form has been made only by way of example and that numerouschanges in the details of construction and the combination andarrangement of parts may be resorted to without departing from thespirit and scope of the invention.

What is claimed is:
 1. An aqueous disinfectant, comprising: an aqueoussolution of silver citrate and citric acid produced by a processcomprising the step of electrolytically generating silver ions in asolution of citric acid and water with the silver ions reacting with thecitric acid to form electrolytically generated silver citrate having aconcentration greater than the concentration of a non-electrolyticallygenerated silver citrate within a similar or same solution of citricacid and water.
 2. An aqueous disinfectant as set forth in claim 1,wherein the electrolytically generated silver forms an organic metalcomplex with the citric acid.
 3. An aqueous disinfectant as set forth inclaim 1, wherein the electrolytically generated silver forms a chelatedorganic metal complex with the citric acid.
 4. An aqueous disinfectantas set forth in claim 1, wherein the citric acid has a finalconcentration greater than 1.0% citric acid by volume.
 5. An aqueousdisinfectant as set forth in claim 1, wherein the citric acid has afinal concentration greater than 1.0% citric acid by volume and with theelectrolytically generated silver citrate having a concentration equalto or greater than 5 parts per million silver.
 6. An aqueousdisinfectant as set forth in claim 1, wherein the electrolyticallygenerated silver forms a complex with the citric acid of (Ag(CA)_(X)⁺(Cit)⁻), wherein CA is (C₆H₈O₇—H₂O) and wherein (Cit)⁻ is (C₆H₇O₇)⁻,wherein said (C₆H₇O₇)⁻ represents a citric acid chemical structure andsaid (C₆H₈O₇) represents a citric acid chemical structure, and wherein Xis an integer.
 7. An aqueous disinfectant as set forth in claim 1,wherein the electrolytically generated silver forms a complex with thecitric acid of (Ag⁺Cit⁻), wherein Cit⁻ is (C₆H₇O₇)⁻ and represents acitrate chemical structure.
 8. A process of making a disinfectant,comprising the step of: electrolytically generating silver ions in asolution of citric acid and water with the silver ions reacting with thecitric acid to create electrolytically generated silver citrate having aconcentration greater than the concentration of a non-electrolyticallygenerated silver citrate within a similar or same solution of citricacid and water.
 9. The process of making a disinfectant as set forth inclaim 8, wherein the step of electrolytically generating silver includeselectrolytically generating silver for forming an organic metal complexwith the citric acid.
 10. The process of making a disinfectant as setforth in claim 8, wherein the step of electrolytically generating silverincludes electrolytically generating silver for forming a chelatedorganic metal complex with the citric acid.
 11. The process of making adisinfectant as set forth in claim 8, wherein the step ofelectrolytically generating silver includes electrolytically generatingsilver for forming a complex with the citric acid of (Ag(CA)_(X) ⁺(Cit)⁻), wherein CA is (C₆H₈O₇—H₂O) and wherein (Cit)⁻ is (C₆H₇O₇)⁻,wherein said (C₆H₇O₇)⁻ represents a citrate chemical structure and said(C₆H₈O₇) represents a citric acid chemical structure, and wherein X isan integer.
 12. The process of making a disinfectant as set forth inclaim 8, wherein the step of electrolytically generating silver includeselectrolytically generating silver for forming a complex with the citricacid of (Ag⁺Cit⁻), wherein Cit⁻ is (C₆H₇O₇)⁻ and represents a citratechemical structure.